docs: def htmlhelp():
      """make HTML files and a HTML help project"""
      build('htmlhelp', 'Now you can run HTML Help Workshop with the .hhp '
                        'project file in {}.')
      print('Running HTML Help Workshop...')
      builddir = os.path.join(BUILDDIR, 'htmlhelp')
      rc = subprocess.call(['hhc', os.path.join(builddir, 'rinohtype.hhp')])
      if rc != 1:
          print('Error running HTML Help Workshop. Aborting.')
          sys.exit(1)
      print('HTML Help Workshop finished; the CHM file is in {}.'
            .format(builddir))